An example of conventional fuel cell system is shown in FIG. 6. In the system, a desulfurizer 2 is supplied with a raw fuel 1 such as natural gas, town gas, methanol, LPG, butane or the like, and here the raw fuel is desulfurized. The raw material having passed through the desulfurizer is pressurized by a pressure pump 10, and supplied to a reformer 3, to generate a reformed gas containing hydrogen, carbon dioxide and carbon monoxide. The gas having passed through the reformer 3 is supplied to a CO transformer 4 and, here, carbon monoxide contained in the reformed gas is transformed into carbon dioxide. The gas having passed through the CO transformer 4 is supplied to a CO remover 5 and, here, non transformed carbon monoxide contained in the gas having passed through the CO transformer 4 is removed.
Hydrogen rich reformed gas after the removal of carbon monoxide having passed through the CO remover 5 is supplied to a fuel cell 6. The fuel cell 6 comprises a fuel pole 6a, an oxidizer pole 6b and a cooling portion 6c and the aforementioned hydrogen is supplied to the fuel pole 6a. The hydrogen reacts with oxygen contained in the air supplied into a water tank 21 through a fan 11, humidified and then supplied to the oxidizer pole 6b, generating electricity.
For instance, when the fuel cell 6 uses a solid polymer electrolyte film, the solid polymer electrolyte film is humidified with moisture contained in the humidified air supplied to the oxidant pole 6b, for improving the ion electric conductivity.
The reformer 3 includes a burner 12 which is supplied with raw fuel through a pipe 13, supplied with air through a fan. 14 and supplied with non reacted hydrogen having passed the fuel pole 6a, through the pipe 15. When the system is started, the burner 12 is supplied with raw fuel through the pipe 13 and, at the same time, supplied with air through the fan 14 and, after the start, in case where the system stabilizes, the raw fuel supply is cut and the burner 12 is supplied with non reacted hydrogen having passed the fuel pole 6a, through the pipe 15.
Chemical reactions having a predetermined reaction temperature take place in the aforementioned reformer 3, CO transformer 4, CO remover 5 and fuel cell 6. The chemical reaction in the reformer 3 being endothermic, the chemical reaction is performed all the way heating with the burner 12.
The chemical reaction taking place in the CO transformer 4 and CO remover 5 being exothermic, for instance in the CO remover 5, combustion gas is generated by burning a not shown burner only during the system start, the temperature of the CO remover 5 is heated to the reaction temperature by the heat of the combustion gas generated at this moment, and during the operation, it is cooled so that the temperature does not elevated to the reaction temperature or higher by the heat of the exothermic reaction.
Each heat exchanger 18, 19 and 20 is connected respectively between the aforementioned reformer 3 and CO transformer 4, between CO transformer 4 and CO remover 5, and between CO remover 5 and fuel cell 6.
Water from a water tank 21 circulates through respective heat exchangers 18, 19, 20 through pumps 23, 24, 25 and the gas having passed through the reformer 3, CO transformer 4, CO remover 5 is cooled respectively by these waters.
Water from the water tank 21 circulates through the cooler section 6c of the fuel cell 6 through a pump 48, and the fuel cell 6 is cooled with the water. 26 indicates an exhaust system of the oxidant pole 6b of the fuel cell 6.
A heat exchanger 17 is connected to an exhaust system 31 of the aforementioned reformer 3, and when the water of the water tank 21 is supplied through a pump 22, it becomes moisture vapor in the heat exchanger 17, and the moisture vapor is mixed with the raw material and supplied to the reformer 3.
In the aforementioned conventional system S, air (the atmosphere air) around the fuel cell is supplied to the water tank 21 through the fan 11, humidified and supplied to the oxidant pole 6b as reaction air. Consequently, a trace of NOx, SOx, cyanides, sulfates, aromatics, ammonium, organic solvents or the other impurities exerting bad effects on the cell characteristics contained in the air (the atmosphere air) is once removed by the water reserved in the water tank 21. However, when the operation time is prolonged, the concentration of impurities in the water increases, and impurities in the air passing through the water tank 21 are not removed no more, for supplying the oxidant pole 6 with air containing impurities as reaction air.
The aforementioned impurities contained in the reaction air arrive at the electrode catalyst layer permeating through the electrode medium with oxygen in the air, come into contact with the electrolyte and provoke a chemical reaction, and the chemical reaction alter the electrolyte and deteriorate functions as electrolyte and, at the same time, inhibit the oxygen absorbing function of the electrode catalyst, and these causes provoke problems such as deterioration of cell characteristics or life characteristics of the fuel cell.
Besides, problems of bad effects due to the impurities contained in such reaction air were not limited to a fuel cell using the solid polymer electrolyte film, but encountered similarly in the other fuel cells such as phosphoric acid type fuel cell.
The present invention has an object of solving conventional problems, preventing cell characteristics and life characteristics of a fuel cell from lowering by composing to supply the oxidant pole 6b of the fuel cell 6 with reaction air, preliminarily removing a trace of inorganic and organic dust, aromatics, volatile components of paint, CO, NOx, SOx, cyanides, sulfates, aromatic compounds, ammonium or the other harmful substances exerting bad effects on the cell characteristics contained in the air (the atmosphere air), and providing a fuel cell apparatus of high reliability, long life and high durability.